Cyclops

A cyclops is a small magnifying lens fitted on the crystal above the date window, making the date easier to read.

It's a signature detail on several well-known references, and its alignment and magnification are among the things experienced buyers check, since poorly made copies often get them wrong.

Check that the cyclops sits centred over the date and magnifies it clearly.

On a pre-owned watch, a scratched or chipped cyclops is usually a replacement rather than a repair, which is a modest cost to note in your offer. Watches that should have a cyclops but don't, or have one that doesn't sit right, can indicate a replaced crystal.